Tire non-uniformity relates to the symmetry (or lack of symmetry) relative to the tire's axis of rotation in mass, geometric or stiffness characteristics. Conventional tire building methods unfortunately have many opportunities for producing non-uniformities in tires. During rotation of the tires, non-uniformities present in the tire structure produce periodically-varying forces at the wheel axis. Tire non-uniformities are important when these force variations are transmitted as noticeable vibrations to the vehicle and vehicle occupants. These forces are transmitted through the suspension of the vehicle and may be felt in the seats and steering wheel of the vehicle or transmitted as noise in the passenger compartment. The amount of vibration transmitted to the vehicle occupants has been categorized as the “ride comfort” or “comfort” of the tires.
Tire uniformity characteristics, or attributes, are generally categorized as dimensional or geometric variations (radial run out (RRO) and lateral run out (LRO)), mass variance, and rolling force variations (radial force variation, lateral force variation and tangential force variation, sometimes also called longitudinal or fore and aft force variation). Uniformity measurement machines often calculate the above and other uniformity characteristics by measuring force at a number of points around a tire as the tire is rotated about its axis. The obtained measurements can generally include a composite waveform representative of tire uniformity, which can be decomposed into many respective harmonic contributions.
The respective tire harmonics obtained from a measured uniformity waveform can be analyzed in accordance with known processing techniques in order to improve uniformity. One example of improving uniformity is implemented by altering the relative angular position of known manufacturing components in a tire to reduce the magnitude of the measured uniformity parameter for one or more tire harmonics of interest. However, this type of uniformity analysis may be hindered by the impact of process effects whose periodic contributions to the composite uniformity waveform are not identical to the tire harmonics, resulting in poorer compensations and adjustments.
The present disclosure provides new techniques that help identify different causes of uniformity, including those due to cyclic elements in the tire manufacturing process whose effects are not identical in wavelength to any particular tire harmonic. Identification of such uniformity contributions can help improve uniformity analysis as well as the tire building process. Although known technologies for tire uniformity improvement have been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.